function does not exist

I'm getting the following error all throughout my PHP log: [warning] [Unknown][0]: Unknown(): Unable to call () - function does not exist I'm not sure it's going to survive the mailing but it appears to be a tab character after the 'call' and before the '()'. I've spent days (not consecutively) trying to track down this eror but have had absolutely no luck. Has anyone else experienced a problem like this? If so, what was causing it for you and what was your solution? thnx, Chris